A Google Adwords tool to get more clicks but waste less money. Using Google's exact match option, you miss many clicks. Using the broad match option, "red cars" would match "red apples" and "blue cars". Use this tool to match only valuable phrases. Other tools just generate phrases in random order without consideration for certain keywords being definitely needed for each phrase and others being option, this can create more variations than Google will even allow for advertising. For example, you may want "red cars" where the color is optional, but the word cars is not because you wouldn't want to pay for ads for just "red".